TAURA SYNDROME IN PENAEUS-VANNAMEI - DEMONSTRATION OF A VIRAL ETIOLOGY

Taura syndrome (TS) was hypothesized to be caused by a virus and prove n experimentally by meeting the criteria of Rivers' postulates. This w as accomplished through 3 serial infectivity studies utilizing specifi c-pathogen-free Penaeus vannamei as the host for the TS virus (TSV). T est animals were infected via intramuscular injection with either a cr ude or cell-free suspension of the virus. The source of the crude homo genate was TSV-infected Ecuadorian P. vannamei, which were collected d uring August 1993. Both types of viral inocula caused cumulative morta lities of 73 to 87% among treatment groups. Diagnosis of TS was based on histological analysis of moribund shrimp collected during each expe riment. All moribund shrimp, collected between 1 to 3 d post-injection , demonstrated moderate to severe pathognomonic TS lesions. Both gross external and histological lesions, characteristic of chronic phase TS , were observed in 25 to 100% of all survivors. Virions with a buoyant density of approximately 1.337 g ml(-1), icosahedral morphology, and a diameter of 31 to 32 nm, characteristics which suggest that TSV is a member of either the Picornaviridae or Nodaviridae, were recovered fr om the dead shrimp collected during each of the 3 infectivity studies. Comparisons of TSV samples isolated from naturally infected P. vannam ei from Hawaii (USA) and Ecuador indicate that the same virus was resp onsible for the TS epizootics in both of these shrimp growing regions.